Optical waveguide fibers (optical fibers) are a well-known transmission medium used in optical communication systems. Fiber draw manufacturing techniques are known wherein the optical fiber is drawn from an optical fiber preform and wound onto a spool. In the past, the drawing of optical fiber has typically involved winding of the fiber onto bulk spools that may hold up to 400 km of fiber. The bulk spool is then typically manually transported to an off-line rewinding machine that is threaded manually by an operator. The off-line machine rewinds fiber from the bulk spool to a plurality of smaller shipping spools. Prior to or during the transfer of the fiber from the bulk spool to the smaller shipping spools, various tests are conducted on the fiber. For example, the same machine used to wind the fiber from the bulk spool to the shipping spool is also commonly employed to apply a predetermined minimum level of stress (typically 100 kpsi) to the fiber to make sure the fiber meets the minimum strength requirements. This application of stress is commonly called screening or proof testing. The machine stops winding to the shipping spool when screening breaks occur, and the operator must then manually rethread the machine again and begin winding the fiber onto a new spool.
It would be desirable to conduct tensile strength proof testing on the fiber during the fiber draw process, before it is wound onto a storage spool, which preferably is a shipping spool. However, with the high draw speeds (e.g. greater than 20-25 m/s) employed in some of today's fiber manufacturing operations, such online proof testing has not been achievable. For one thing, online screening would increase the number of fiber breaks in the fiber at the draw, due to the added tensile stress applied to the fiber to proof test it. In addition, because the fiber draw process cannot be stopped, there would be a great deal of lost fiber while the operator rethreaded the online tensile screening equipment. Of course at the higher draw speeds (e.g. greater than 20 m/s) employed in many of today's fiber draw processes, the fiber being threaded would somehow also have to keep up with the length of fiber being fed by the fiber draw process. Also, because of the time involved with threading conventional tensile testing apparatus, using conventional techniques a great deal of fiber would be lost during the rethreading operation. As a result, manufacturers have thus far instead had to resort to manufacturing processes wherein they draw the fiber at lower draw tensions onto relatively large (e.g. can store 400 km or more) bulk spools. These fiber on these bulk spools is then proof tested off-line, during or prior to its being wound onto smaller shipping spools.